Put the book ______ it should be when you’ve finished reading it.
| A.how | B.which | C.where | D.who | 
Experiments of this kind _______in both the U.S. and Europe well before the Second World War started.
| A.have conducted | B.have been conducted | 
| C.had conducted | D.had been conducted | 
Robert is said________ abroad, but I don’t know what country he studied in.
| A.to have studied | B.to study | 
| C.to be studying | D.to be studied | 
We live in an age ________ more information is available with greater ease than ever before.
| A.why | B.when | C.to whom | D.on which | 
Tom took a taxi to the airport, only _____ his plane high up in the sky.
| A.finding | B.to find | C.being found | D.to have found | 
The market competition is fierce, but our products have great advantage ______ quality and price.
| A.in place of | B.in view of | C.in case of | D.in terms of |